Much like a golf clap in idea, but used differently: To offer a short, polite chuckle to someone as an acknowledgement that they said something THEY think is amusing, but it really isn't. To help someone not feel uncomfortable or embarrassed by politely laughing at their stupid joke.

"OMG, that guy I'm dating said that stupid duck-under-one-arm joke lastnight in front my friends! I had to give him the golf laugh just so he didn't look like a complete idiot!"